207 lines
6.4 KiB
Markdown
207 lines
6.4 KiB
Markdown
# Generating Bash Completions For Your Own cobra.Command
|
|
|
|
Generating bash completions from a cobra command is incredibly easy. An actual program which does so for the kubernetes kubectl binary is as follows:
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"io/ioutil"
|
|
"os"
|
|
|
|
"github.com/GoogleCloudPlatform/kubernetes/pkg/kubectl/cmd"
|
|
)
|
|
|
|
func main() {
|
|
kubectl := cmd.NewFactory(nil).NewKubectlCommand(os.Stdin, ioutil.Discard, ioutil.Discard)
|
|
kubectl.GenBashCompletionFile("out.sh")
|
|
}
|
|
```
|
|
|
|
That will get you completions of subcommands and flags. If you make additional annotations to your code, you can get even more intelligent and flexible behavior.
|
|
|
|
## Creating your own custom functions
|
|
|
|
Some more actual code that works in kubernetes:
|
|
|
|
```bash
|
|
const (
|
|
bash_completion_func = `__kubectl_parse_get()
|
|
{
|
|
local kubectl_output out
|
|
if kubectl_output=$(kubectl get --no-headers "$1" 2>/dev/null); then
|
|
out=($(echo "${kubectl_output}" | awk '{print $1}'))
|
|
COMPREPLY=( $( compgen -W "${out[*]}" -- "$cur" ) )
|
|
fi
|
|
}
|
|
|
|
__kubectl_get_resource()
|
|
{
|
|
if [[ ${#nouns[@]} -eq 0 ]]; then
|
|
return 1
|
|
fi
|
|
__kubectl_parse_get ${nouns[${#nouns[@]} -1]}
|
|
if [[ $? -eq 0 ]]; then
|
|
return 0
|
|
fi
|
|
}
|
|
|
|
__custom_func() {
|
|
case ${last_command} in
|
|
kubectl_get | kubectl_describe | kubectl_delete | kubectl_stop)
|
|
__kubectl_get_resource
|
|
return
|
|
;;
|
|
*)
|
|
;;
|
|
esac
|
|
}
|
|
`)
|
|
```
|
|
|
|
And then I set that in my command definition:
|
|
|
|
```go
|
|
cmds := &cobra.Command{
|
|
Use: "kubectl",
|
|
Short: "kubectl controls the Kubernetes cluster manager",
|
|
Long: `kubectl controls the Kubernetes cluster manager.
|
|
|
|
Find more information at https://github.com/GoogleCloudPlatform/kubernetes.`,
|
|
Run: runHelp,
|
|
BashCompletionFunction: bash_completion_func,
|
|
}
|
|
```
|
|
|
|
The `BashCompletionFunction` option is really only valid/useful on the root command. Doing the above will cause `__custom_func()` to be called when the built in processor was unable to find a solution. In the case of kubernetes a valid command might look something like `kubectl get pod [mypod]`. If you type `kubectl get pod [tab][tab]` the `__customc_func()` will run because the cobra.Command only understood "kubectl" and "get." `__custom_func()` will see that the cobra.Command is "kubectl_get" and will thus call another helper `__kubectl_get_resource()`. `__kubectl_get_resource` will look at the 'nouns' collected. In our example the only noun will be `pod`. So it will call `__kubectl_parse_get pod`. `__kubectl_parse_get` will actually call out to kubernetes and get any pods. It will then set `COMPREPLY` to valid pods!
|
|
|
|
## Have the completions code complete your 'nouns'
|
|
|
|
In the above example "pod" was assumed to already be typed. But if you want `kubectl get [tab][tab]` to show a list of valid "nouns" you have to set them. Simplified code from `kubectl get` looks like:
|
|
|
|
```go
|
|
validArgs []string = { "pod", "node", "service", "replicationcontroller" }
|
|
|
|
cmd := &cobra.Command{
|
|
Use: "get [(-o|--output=)json|yaml|template|...] (RESOURCE [NAME] | RESOURCE/NAME ...)",
|
|
Short: "Display one or many resources",
|
|
Long: get_long,
|
|
Example: get_example,
|
|
Run: func(cmd *cobra.Command, args []string) {
|
|
err := RunGet(f, out, cmd, args)
|
|
util.CheckErr(err)
|
|
},
|
|
ValidArgs: validArgs,
|
|
}
|
|
```
|
|
|
|
Notice we put the "ValidArgs" on the "get" subcommand. Doing so will give results like
|
|
|
|
```bash
|
|
# kubectl get [tab][tab]
|
|
node pod replicationcontroller service
|
|
```
|
|
|
|
## Plural form and shortcuts for nouns
|
|
|
|
If your nouns have a number of aliases, you can define them alongside `ValidArgs` using `ArgAliases`:
|
|
|
|
```go`
|
|
argAliases []string = { "pods", "nodes", "services", "svc", "replicationcontrollers", "rc" }
|
|
|
|
cmd := &cobra.Command{
|
|
...
|
|
ValidArgs: validArgs,
|
|
ArgAliases: argAliases
|
|
}
|
|
```
|
|
|
|
The aliases are not shown to the user on tab completion, but they are accepted as valid nouns by
|
|
the completion algorithm if entered manually, e.g. in:
|
|
|
|
```bash
|
|
# kubectl get rc [tab][tab]
|
|
backend frontend database
|
|
```
|
|
|
|
Note that without declaring `rc` as an alias, the completion algorithm would show the list of nouns
|
|
in this example again instead of the replication controllers.
|
|
|
|
## Mark flags as required
|
|
|
|
Most of the time completions will only show subcommands. But if a flag is required to make a subcommand work, you probably want it to show up when the user types [tab][tab]. Marking a flag as 'Required' is incredibly easy.
|
|
|
|
```go
|
|
cmd.MarkFlagRequired("pod")
|
|
cmd.MarkFlagRequired("container")
|
|
```
|
|
|
|
and you'll get something like
|
|
|
|
```bash
|
|
# kubectl exec [tab][tab][tab]
|
|
-c --container= -p --pod=
|
|
```
|
|
|
|
# Specify valid filename extensions for flags that take a filename
|
|
|
|
In this example we use --filename= and expect to get a json or yaml file as the argument. To make this easier we annotate the --filename flag with valid filename extensions.
|
|
|
|
```go
|
|
annotations := []string{"json", "yaml", "yml"}
|
|
annotation := make(map[string][]string)
|
|
annotation[cobra.BashCompFilenameExt] = annotations
|
|
|
|
flag := &pflag.Flag{
|
|
Name: "filename",
|
|
Shorthand: "f",
|
|
Usage: usage,
|
|
Value: value,
|
|
DefValue: value.String(),
|
|
Annotations: annotation,
|
|
}
|
|
cmd.Flags().AddFlag(flag)
|
|
```
|
|
|
|
Now when you run a command with this filename flag you'll get something like
|
|
|
|
```bash
|
|
# kubectl create -f
|
|
test/ example/ rpmbuild/
|
|
hello.yml test.json
|
|
```
|
|
|
|
So while there are many other files in the CWD it only shows me subdirs and those with valid extensions.
|
|
|
|
# Specifiy custom flag completion
|
|
|
|
Similar to the filename completion and filtering using cobra.BashCompFilenameExt, you can specifiy
|
|
a custom flag completion function with cobra.BashCompCustom:
|
|
|
|
```go
|
|
annotation := make(map[string][]string)
|
|
annotation[cobra.BashCompFilenameExt] = []string{"__kubectl_get_namespaces"}
|
|
|
|
flag := &pflag.Flag{
|
|
Name: "namespace",
|
|
Usage: usage,
|
|
Annotations: annotation,
|
|
}
|
|
cmd.Flags().AddFlag(flag)
|
|
```
|
|
|
|
In addition add the `__handle_namespace_flag` implementation in the `BashCompletionFunction`
|
|
value, e.g.:
|
|
|
|
```bash
|
|
__kubectl_get_namespaces()
|
|
{
|
|
local template
|
|
template="{{ range .items }}{{ .metadata.name }} {{ end }}"
|
|
local kubectl_out
|
|
if kubectl_out=$(kubectl get -o template --template="${template}" namespace 2>/dev/null); then
|
|
COMPREPLY=( $( compgen -W "${kubectl_out}[*]" -- "$cur" ) )
|
|
fi
|
|
}
|
|
```
|